Patient tables, particularly gurneys, are ubiquitous throughout hospitals. Gurneys are well known for transporting patients and useful for a variety of specialized tasks. For example, gurneys have been used to receive traumatized patients in emergency situations, transport patients from one location to another, as well as serve as operating tables during surgery. In some cases certain medical imaging equipment, such as ultrasound units can be used on patients lying on gurneys without moving the patient, because in such cases the imaging equipment is readily positionable with respect to the patient.
Larger imaging equipment, such as CT, MRI and PET scan systems, however, are usually too large to move relative to a patient. A CT scan system, for example, includes supporting structure, usually in the form of a yoke, for supporting a gantry. The latter includes a frame, which in turn supports a centrally apertured disk for rotation relative to the frame about a rotation axis. Imaging equipment is mounted on the disk so as to rotate with the disk about its center aperture. The imaging equipment includes an X-ray source which may provide periodic pulses or continuous wave radiation. In third generation CT scan machines, X-rays are detected by a detector array mounted on the disk diametrically across from the source, while in fourth generation machines X-rays emitted by the source are detected by a plurality of detectors fixed circumferentially around the frame. In both types of machines the detectors are positioned and aligned with respect to the source so that the ray paths of the X-rays generated by the source and subsequently sensed by the detectors are all disposed within a common mean scanning plane (perpendicular to the axis of rotation of the disk).
A patient must be positioned through the central aperture of the disk so that the scanning plane passes through a select part of the patient for which an image is to be formed. This arrangement provides information corresponding to variations in X-ray absorption measured by the detectors during rotation of the disk about the patient. Upon known (Radon) mathematical processing of the information, visual images can be "back projected", each representing density distribution of a slice along the scanning plane, through the part of the patient positioned in the plane between the source and detectors.
The formation of a meaningful image depends, inter alia, upon the pertinent part of the patient being positioned within the central aperture of the disk and remaining immobile in that position during scanning. The quality of the data also critically depends upon (1) the imaging components (i.e., the source, and in the case of third generation machines also the detectors) positioned on the disk moving through a smooth circular path about a common point during a scan, i.e., the image "center", or "isocenter" (which should be coincident with the axis of the disk), and (2) the image center remaining fixed relative to the patient so that no relative, lateral movement occurs between the patient and the imaging components. Since even minor relative lateral movement between the patient and the imaging components within the scanning plane during a scan can cause errors resulting in faulty or erroneous images, such apparatus has been provided as massively reinforced devices often weighing a ton or more.
MRI and PET equipment exhibits many similar characteristics, particularly being large and heavy because such equipment employs large magnets. As a result such massive devices are not readily manipulable to adjust the location of the disk aperture to the position of the patient. In addition, since imaging requires the proper positioning of the patient within the equipment, the table upon which the patient rests must usually be translated in a direction parallel to the axis of the imaging components. Accordingly, such equipment is typically provided with its own table coupled to the scanning equipment such that the table moves through the center aperture so as to properly position the patient so that the patient can be scanned.
Too often, however, a patient who is in need of a scan is usually reposed on a gurney, or other type of patient table, in a traumatized state, because, for example, of an injury or because he or she is having surgery performed. In such cases it is necessary to transfer the patient from the gurney to the table of the scanner which can exacerbate the trauma and cause harm to the patient. This is particularly a problem in surgery, for example, where a surgeon may want to know whether he or she has completely removed cancerous tissue, or is entering the brain at a prescribed location. Under such circumstances it would be necessary to suture the patient to move him or her to the location of a CT scanner, move the patient off the gurney to the scan table, perform the scan, move the patient back to the gurney, and then move the patient back to the operating room if further surgical intervention is warranted. Because of the possible trauma that can result from such patient movement during such surgery, such scans are usually not performed.
Accordingly, at least one object of the present invention is to provide a patient trauma table, preferably in the form of a gurney, which can support a traumatized patient and also function as a table for use with medical imaging equipment.
Thus, in accordance with one aspect of the present invention, an improved patient table, preferably in the form of a wheel supported gurney, is provided. The table includes a top panel or palette for supporting a trauma patient. The top panel is extendable laterally relative to a supporting base so that it can extend into the central aperture of medical imaging equipment such as a CT scanner.
Typical gurneys now found in hospitals are wheeled so they may be easily pushed around by personnel (including small women) in a hospital or clinic. The Federal Drug Administration requires that a gurney should be able to support a 350 pound patient. The table itself typically weighs approximately 250 to 350 pounds and even with a 350 pound patient should be easy to push.
A typical gurney table is seven feet long. It has been determined that when designing a gurney in accordance with the present invention so that it includes an extendable top that can extend into the central aperature of medical imaging equipment such a CT scanner, when such a table is positioned adjacent the medical imaging equipment, a substantial portion of the top should be able to be laterally extended, e.g. , as much as five feet, out from the supporting base, with the remaining portion, e.g., only two feet, of the top supported over the base. The patient on the panel is thus cantilevered relative to the table base. A particular concern, however, is that a patient extended out into the imaging equipment may become frightened, try to push against the imaging equipment and get off the table from the cantilevered end. This could easily cause the table to tip and possibly injure the patient.
Accordingly, it is another object of the present invention to provide an improved system for stabilizing the relation between a patient trauma table and the medical imaging equipment.
Another object of the present invention is to provide a system for stabilizing the table relative to the imaging equipment so that even excessive patient load can be safely controlled under emergency conditions.
Yet, other objects of the present invention are to provide such a stabilization system in which the table can be fixed relative to the frame of the imaging equipment in order to insure that there is no relative movement between the table and imaging equipment during the imaging process, and to provide such a stabilization system wherein the position of the table top relative to the frame can readily be ascertained.
The objects of the present invention are effected generally by the provision of a system for stabilizing a table having a top including a patient-supporting panel capable of being moved into a cantilevered position relative to the supporting base of the table so that a portion of the panel is disposed in an imaging position with respect to medical imaging equipment.
In the preferred embodiment of the system, the supporting table base includes a pair of vertically extendible devices such as screw jacks for raising, lowering and/or tilting the table top relative to the imaging equipment, the vertical extensible devices each preferably being controlled by a stepper motor. The supporting table base is designed to be attachable to the supporting structure of the imaging equipment to establish a fixed relation between the table and the imaging equipment that allows substantially no relative movement between them. A stabilizing device preferably includes a support arm having a roller at one end. The support arm is preferably fixed relative to the frame of the imaging equipment for incremental vertical movement by a stepper motor so that the roller is movable in and out of contact with the underside of the cantilevered end of the patient-supporting panel. For safety reasons, means, preferably in the form of a strain gauge, are coupled to the support arm for providing an indication of when to stop the stepper motor from advancing the support arm further against the table patient-supporting panel when a predetermined roller contact pressure is exceeded. A counter is provided for counting the steps provided by the stepper motor driving the support arm so that the precise position of the table top with respect to the components of the imaging equipment can be determined.
Other objects of the present invention will in part be more evident and will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts exemplified in the following detailed disclosure and the scope of the application of which will be indicated in the claims.